No, to both ideas.

• The fact that a creature has hexproof has no bearing on the spell the creates the creature; see "Can I give a creature spell hexproof to prevent it from being countered?".
• A spell which "cannot be countered" stops only effects which say "counter target spell", for example Counterspell. It does not stop:
  • The spell being exiled, for example with Mindbreak Trap
  • The spell being returned to hand, for example with Unsubstantiate
  • The spell being put on top of its owner's library, for example with Memory Lapse
  • The turn ending while the spell is still on the stack, for example with Discontinuity

No, to both ideas.

• The fact that a creature has hexproof has no bearing on the spell the creates the creature; see "Can I give a creature spell hexproof to prevent it from being countered?".
• A spell which "cannot be countered" stops only effects which say "counter target spell", for example Counterspell. It does not stop:
  • The spell being exiled, for example with Mindbreak Trap
  • The spell being returned to hand, for example with Unsubstantiate
  • The spell being put into its owner's library, for example with Aether Gust
  • The turn ending while the spell is still on the stack, for example with Discontinuity

No, to both ideas.

• The fact that a creature has hexproof has no bearing on the spell the creates the creature; see "Can I give a creature spell hexproof to prevent it from being countered?".
• A spell which "cannot be countered" stops only effects which say "counter target spell", for example Counterspell. It does not stop:
  • The spell being exiled, for example with Mindbreak Trap
  • The spell being returned to hand, for example with Unsubstantiate
  • The turn ending while the spell is still on the stack, for example with Discontinuity

No, to both ideas.

• The fact that a creature has hexproof has no bearing on the spell the creates the creature; see "Can I give a creature spell hexproof to prevent it from being countered?".
• A spell which "cannot be countered" stops only effects which say "counter target spell", for example Counterspell. It does not stop:
  • The spell being exiled, for example with Mindbreak Trap
  • The spell being returned to hand, for example with Unsubstantiate
  • The spell being put on top of its owner's library, for example with Memory Lapse
  • The turn ending while the spell is still on the stack, for example with Discontinuity