Can I use another Sim Card to Activate my iPhone, and then use my upcoming Sim Card when it arrives?

If you phone is SIM unlocked, then yes.

Not necessarily. Did you buy it unlocked? Apple sells both unlocked and locked phones. What price did you pay?

What does the receipt say? It will usually say it is inlocked on the receipt.

no not unless you bought it spc. to be factory unlocked

where the price typically is 2 times that of locked phones as the carrier pay

the rest

Which model? And capacity.