Does my minor child get all of his paid taxes back?

Being a "minor" has nothing to do with it.  Some minors make a lot of money and can owe tax due.  But they can get a refund from the amounts in box 2 or box 17 of their W-2 depending on how much they earned.

MY DEPENDENT HAD A JOB

If your dependent has a W-2 for his after-school job, summer job, etc. you do not include the information on your own return. You can still claim your child as a dependent on your own return.  He/she can file his own return for a refund of some of his withheld wages (he won’t get back anything for Social Security or Medicare), but MUST indicate on it that he can be claimed as a dependent on someone else’s return.  (Supervise this closely or prepare it for him!)

If your dependent’s earnings were over $400 and were reported on a 1099Misc or 1099NEC then he must file a return and pay self-employment tax for Social Security and Medicare.

No, not always.  The standard deduction for minor children claimed on their parents returns will determine if there is any taxable income. As well as the amount and type of income the minor children may have. The link below will give more insight for your specific situation.

• At what income does a minor have to file an income tax return?

Basics:

• A minor who may be claimed as a dependent, needs to file a return if their income exceeds their Standard Deduction.
• A minor who earns less than $14,600 in 2024 will usually not owe taxes but may choose to file a return to receive a refund of tax withheld from their earnings.
• A child who earns $1,300 or more (tax year 2024) in "unearned income,” such as dividends or interest, needs to file a tax return.
• A minor who makes more than $400 (tax year 2024) in self-employment income will typically have to pay Social Security or Medicare taxes, regardless of their total earnings.

@thegreatginch 

The taxpayer (minor or not) can only get  back the withholding in box 2 of the W-2.  You can not get back the withholding in box  4 (social security) and box 6 (Medicare).  

Whether you get  any of the box 2 amount depends on your total income.  Dependents may a;so get  a reduced standard deduction if they have unearned income.