See: BIOS Beep Codes for Desktop Boards
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Intel® Desktop Board | DZ77GA-70K | Technical Product Specification (PDF)
page 81 shows the beep codes; pages 83 - 87 show the post codes
I don't see 4 beeps in that manual, 4 beeps is listed in the first reference in the legacy board table. Intel states that the board is no longer supported, so that probably makes it legacy.
The code 10 seems to indicate Resuming from S2
Are there any LED codes?
When you reseated your CPU, did you apply new thermal paste?
You said you tested on RAM in all slots, did you test all RAM in each slot ... or at least one other stick in each slot?
Was there a power outage overnight? The components aren't that old.