Can I use plywood to replace floorboards

So, your builder's used plywood to patch up your rotten floorboards, right? Now, plywood can be a good choice for this, particularly if it's a good-quality, thick one. It's sturdy, flat, and can create a solid base. However, there are a few things you need to take into account. Firstly, if the plywood is exposed to a lot of moisture – say, from a leak or spill – it can warp or delaminate over time. Kitchens, as we know, can get a bit damp now and then. So, the plywood should be well sealed and, ideally, covered with something water-resistant like tiles, especially in a kitchen. Secondly, you've got to consider how it matches with the rest of your floor. If the rest of the floorboards are intact and you're just patching a section, you want to make sure it's level with the rest. Nothing worse than a dodgy trip hazard in your own kitchen, am I right? Lastly, if the rot was caused by something like damp or a leak, make sure you've sorted that out first. No point fixing the floor if the cause of the problem's still there, 'cause it'll just come back. Get that seen to before anything else. So, to wrap it up, yes, plywood can be suitable if it's done right. But always best to get a professional opinion to make sure it's the right solution for your specific situation.

Not really , the ply could delaminate it should be water bonded tounge and groove chipboard or old fashioned floorboards. I would get him to do it again.

I would recommended using cabre flooring which is a tongue and groove chipboard, plywood can delaminate

I agree with all the above, you will need to use a flooring specific tongue and groove chipboard, this should give a very good working area for any flooring company to replace the flooring