You budget is whatever you make it. As long as it's dollar for dollar, it doesn't really matter.

That just sounds like re-budgeting. As long as you're not living beyond your means, I don't see the issue.

the idea is to budget prospectively what you actually need in each category but moving money retrospectively is fine. I wouldn't make too detailed of categories though. I try to keep it buckets >$200 or so. So you could just combine the clothing and makeup budgets in one category.

I do this all the time. I would say it’s allowed. But if you find yourself doing it every month maybe you should reevaluate the category you need to borrow for and make sure you are budgeting the right amount. Doing it as a one off is totally fine tho, shit happens.

>Is this cheating the system?

Not really. A budget just exists to ensure your overall expenses remain below a certain level. Doesn't matter if you have discrete line items for make up, clothing, and haircuts or if you combine all of that into a single "makes me look good" budget.

If you overspend in a certain area, it may make sense to increase the granularity of the budget (i.e. not allowing yourself to spend more than $X amount on Video games, or booze, or whatever you spend too much on)

This is totally allowed. Not only borrowing, but flat out taking/moving money from one category to another. A flat $200/month is not a really good budget for shopping like clothes - some months you may be under $100, but once in a while you may find a good deal or something that fits super well and you want to spend 5 times as much. As long as you're able to cover it from another category without dipping into debt, go for it.

There is a popular budgeting app called "YNAB", and they have a set of 4 guiding principles. This adjustment of categories is number 3 of the 4 rules: https://www.youneedabudget.com/the-four-rules/#rule-three

It is cheating

But in my opinion can be used to save more money if done wisely