Nested COUNTIF / IF formula for data validation workaround

I have a table with several columns for end user entry. Because I'm using formulas in the cells, I can't use data validation (nor VBA), but I still want to let end users know if they've entered data correctly or not, so I created an additional helper column, col. W, to check their entries.

There are 10 questions in Part 1, columns I-R (Q1-Q10), and an addition 4 questions in Part 2, columns S-V (Q11-Q14). The trick is the in column G asks if they are answering only the first 10 (Part 1), and all 10 must be either 'y' or 'n', or if they are answering all 14 questions, the last four answered with either, 'y', 'n', or 'n/a'.

FYI, I have an additional column H (All Yes) which will automatically put y's in questions 1-10 or 1-14, depending on the entry in col. G. So I'm looking at a rather complex, nested IF and COUNTIF formula for column W, that will return either "OK" or "Error." It should return 'OK' if all 14 questions are being answered (no blanks) AND if Q1-Q10 are all answered either y or n AND if Q11-Q14 are answered y, n, or n/a. If there is a blank OR if there is an value other than y or n for Q1-Q10 or a value other than y, n, or n/a for Q11-Q14, then it should return "Error."

In my sample, rows 2-4 should be "OK" in column W, and "Error" should be returned in rows 6 & 7.

sample 1a.xlsx