Grout is starting to come loose on porcelain tile floor

Yes if you have more of the same tile. Now why your grout is cracking is the question. This is usually caused by a flex in the subfloor below the tiles . So yes you can remove the old tiles but it will happen again unless you address the underlying issues.

Definitely need to remove the tiles and when you install new ones to install the first underlayment (like Uncoupling Membrane DITRA )

Yes, it can be repaired!! Loose grout usually means the tile is moving. To fix it properly: Remove the loose grout around the affected tiles Lift and reset the loose tiles using fresh thinest (tile adhesive) Make sure the tiles are level and firmly bonded. After the thinset dries, re-grout the joints. Wipe and seal the grout if needed. If you only re-grout without fixing the loose tile, the grout will break again, so the tile must be secured first.

Yes. First all areas you see the tile loose maybe the tile not glue good with the cement that why the tiles keep loosing if is it, the tile need to remove then install again the re-grout the new one. Secondly if the tile is in good condition that means maybe the grout was not grouting properly you need remove all grout then mix the new grout very nice then re-grout nicely. We can help for that.