Transfer from one subsidiary to another

Hello! I am an employee employed by Company A. My duties involve Company B, a fairly new and small company, smaller than A. Both are subs of a parent company.

Since my tasks revolve around Company B, Company A pays Company B for my salaries since Companies B does not have its own HR team set up yet. Both A and B share the same HR. Almost all employees are under Company A.

There is now new directive that employees employed by A but rendering service to B will now be transferred to B. B will now have its own HR.

My questions are:
1. Is Company B obliged to offer us the same salaries, benefits, and other employee perks (14th month, performance bonus, etc.)?
2. Can we request for Company B to retain my tenure so it will not be reset/back to zero?
3. Are we eligible for separation pay from Company A?
4. It feels as if we do not have a choice but to officially transfer if we wish to continue serving Company B. Can management terminate us from A if we are not willing to transfer to B?

Hope you can shed some light. Thanks in advance.

1. Yes, there shouldn't any diminution of benefits / salary.
2. Connected with #3. If they don't pay you separation pay, then they should continue your tenure.
3. Company's prerogative.
4. If you don't wish to join Company B. You can resign.