Yasakani No Magatama says:

While this card is ready your control cheacks get -1 and your attacks get +1 damage.

Ayame's Scarf says: while this card is ready in your staging area, control values may not be reduced below their printed value.

1. if both are ready. can ayame's scarf stop reducing control check of YNM ?

2. if both are ready. my attack get +1 damage ?

1. Yes, Ayame's Scarf doesn't say anything about whose effect may not lower your checks, so it will prevent the -1

2. Yes, Yasakani doesn't say anything about the +1 requiring the -1 to happen ("And then", etc) so it will still give the +1 damage if the -1 is avoided or prevented somehow.