Inquisitor 1497

[Ripper]

Getting there, but stuck (as usual!)
12 across: Unwontedly lessen pathing now and then to perform one computer operation (10) S?NGL?STE?
15 across: Shelled, with death as a result, in any circumstances (5,2 words) ATON? is it at one and if so could someone explain the word play?
10 down: Intoxicated after conclusion of blind, I've acted destructively whilst going down (10) ??VE?O?B??
9down: Assigned to regions, not starting, indeed, at some future date (6, 2 words) A??DA? is it all day? and if so could someone explain the word play?
Thanks in advance.

[Neveracrossword]

12 Singlestep (a computer term, unknown to me)
10. Divebombed
15 and 19 have thematic stuff involved.

9 D. One Day, at some future time. It's (Z)oned +Ay, indeed.

[dannyk13]

12a.Single step

[Tilly2]

10 d Dive bombed?

[Neveracrossword]

15 A. At All, in any circumstances. It's from F atal ly, with death as a result. It is shelled/using only the centre letters.

Remember that there are clashes.

[Ripper]

Thank you Neveracrossword, dannyk13 & Tilly2