I saw someone on Quora yesterday say that God does not like the idea of things being "unisex". Where do we draw the line of what's okay for both males and females? I understand something like clothes should be masculine and feminine, but what about toys, for example? Can girls play with Hot Wheels and can boys play with dolls? Are toys gendered or are they unisex? Growing up, I didn't like dolls, I liked Hot Wheels. Why do "girl" toys have to be pink, and why do "boy" toys have to be blue? Do colors have gender now? XD... Anyways, I also worry about hair length. I'm not a male, and I prefer to have my hair down to my shoulders, which isn't too short for a female, but is it a sin for men to have long hair? What does Paul mean when he says that long hair on a man is shameful and is against nature (excluding the Nazarite vow), as male hair is thinner and men usually are the ones that go bald. How can a man have long hair without looking like a female? I like to listen to classic rock bands, and a lot of the guys had long hair, and dare I say it, they actually looked good with long hair! We know they are men, but how is long hair on a guy sinful, and in what ways is it sinful? What does shameful exactly mean, and what does it mean to be against nature?
It is an essential skill to work toward (through regular Bible reading) to be able to tell when someone's comment is based on something directly from the Bible or something he/she has deduced from what is in the Bible. Even when a comment is based on something directly from Scripture (which hopefully will have a Bible citation so you can look it up yourself), people interpret the same verses differently. People's deductions from Scripture without direct support in verses sometimes have the quality of hearsay—in other words, just wrong and sometimes harmful! Asking a pastor is sometimes a good idea (or perhaps writing a post in an online forum.

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Until you've been reading the Bible a long time, how you handle this question about what someone said is to be like the Bereans:
Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true. (Acts 17:11, 1984 NIV)
It doesn't take that long before a person can do this with some help. I view your question as seeking that help.
To understand anything written, one must understand the context it was written in. For example, it is important to know how the writer thought his intended audience would understand what he writes. To do this with the Bible, we need to become increasingly familiar with the cultures of the people in the Bible.
It hasn't even been 20 years since tattoos went mainstream. Before then many saw tattoos as indicating a person was a part of some subculture (e.g., motorcycle gang, armed forces). It caused a big controversy in Christian circles for various Scriptural reasons. It was argued that it displeased God, wasn't being a good steward of one's body, not accepting yourself as God made you, and so on. However, it was also said that the negatives associated with it in the Bible were cultural (connected to worshiping false gods, prostitution, etc.), not as important as other questionable things that God permitted, and so forth. What we can safely say, however, is that God does not issue a command anywhere in the Bible not to have tattoos that clearly has nothing to do with culture. Contrast this to one of the ten commandments: not to kill another person. That killing is bad is found all throughout the Bible and is presented as bad to people from many different cultures. In this case, it is easy to see there is principle at work revealing God's nature on the subject. And it follows a principle that Jesus said was the 2nd-most important command (in Mark 12:31):
Do to others as you would have them do to you. (Luke 6:31, 1984 NIV)
All of the unisex matters you mention are culture-based. In other words, God did not say anything directly about them that obviously applies to us today. Even so we need to examine one more thing:
Do not destroy the work of God for the sake of food. All food is clean, but it is wrong for a man to eat anything that causes someone else to stumble. (Romans 14:20, 1984 NIV)
In other words, if a man wearing long hair is going to cause someone to deter or harm their relationship with Jesus, then that man should not wear long hair. This is very dependent on what the people that see and interact with you believe. Keep in mind that one of the most important things about being a Christian is being an example of Jesus' love and character for others (e.g., Gal. 5:22-23) without feeling like we are failing to be perfect. (We do the best we can.) There is another important verse:
Accept him whose faith is weak, without passing judgment on disputable matters. (Romans 14:1, 1984 NIV)
Combining all those ideas, including that God made you as you are, weigh all these issues (sometimes with prayer asking for wisdom from God, cf. James 1:5) to figure out how a specific action applies to
you. How it applies to others
may not be the same as it applies to you.
Even for those that have been reading the Bible a while, I recommend the following book. It is easy to understand:
How to Read the Bible for All Its Worth by Gorden Fee and Douglas Stuart.
Regarding the last couple of questions in your post: Shame is what one experiences when you believe you have done something that will cause or has caused others to reject you when in fact you desire/need their acceptance.
Against nature refers to the natural things that are contrary to God's nature. God made hair. God made hair to grow. There's nothing wrong with those things. Complaints about men having long hair are rooted in what "seems right" by individuals and those in a particular subcultures, and not based on a moral principle revealed by God in the Bible. (You can always ask for the Bible verses they base their conclusion on.)