Guardian Genius 256

[LeenaH]

The instruction for modification is

Select every numbered cell in order

 

What does this mean? 

First Across answer is Navigate. Where should the modification happen? I can't think of any other word with most letters remaining the same. 

Please help. Thanks 

[Lie-in King]

I haven't done it, but I've just looked at the puzzle - do you get a message if you read the letters in the numbered cells from the finished grid in order?

1d, 2d, 3d, 4d, 5d, 6d, 7d, 8a, 9a, 10a, 11a etc...

[Neveracrossword]

Leenah, don't panic! The modifications are only in the first letter, the 'numbered cell' and not every answer needs modified. As the message says, you start with 1 D - the first of the numbered cells.  1 D stays the same, 2 D changes to an H - because I could see that this would give a three-letter word  as 3 D stays the same too. 4 is the same, 5 changes to an A as I could see another word forming.

[Neveracrossword]

Yes, Lie-in King - and I think most people who do crosswords expect to start with the Across entries, but the message here  is ' ... numbered cell...'  It was quite good fun to do, get to the 'release from 50 years ago.

[LeenaH]

Thanks a lot. Got it with all your help.

Thank you very much for answering all my questions patiently.

Special thanks to Neveracrossword and jj109

[Neveracrossword]

LeenaH, glad you got this finished, glad our (little) bit of help proved useful.