Is a refinish possible?

All solid hardwood floors can be resanded and finished professionally. Your floor can also be extended if the other area is lower and can be raised I. E. Latex etc.

Yes you be able to buff floor back up to a nice finish and extend the floor throughout the room. Existing may need to come up to achieve height preference. Another option would be a matching hardwood threshold strip. Thanks john

The first thing: needs to find out if it is "solid hardwood" or "engineering hardwood" if it is the latter; how many times has been restored before as the hardwood layer only can take approximately up to 5-6 depending on how much has been taken from the hard layer, the only way you could check with certainty is to inspect one of the boards and see how much left you have before hitting the next layer down. In regards of the differences of levels; if the existing level (hardwood flooring) is too high it is always beneficial as you could build with different means; sticking thin plywood down, self leveling compound, etc) taking in considerations other meeting up levels (other rooms, main entrance, corridors, etc). Also the floor can be lay continuously without using threshold strip.

Whilst it should be possible to refinish a solid wood floor it would be best to get a professional to take a look. In my experience there are occasionally floors that have very little sandable floor left having been refinished in the past. In terms of extending the floor this too can be possible if the variety of wood is still available and the relevant width (to enable the new floor to be ‘stitched-in’ to the existing floor.