I am a non-EU citizen (Turkish) with a long-stay Romanian visa, and temporary residence card valid until July. Can I travel visa-free to Schengen countries?
Since Romania is only in Schengen by air, after I enter a Schengen country by plane can I travel to another country by train?
I am a non-EU citizen (Turkish) with a long stay Romanian visa, and temporary residence card valid until July. Can I travel visa-free to Schengen countries?
Probably, see Can I travel visa free to Schengen countries with Romanian residence permit? Romania finally joining the Schengen area shouldn't make a difference in that respect (unlike short stay visas).
Since Romania is only in Schengen with airway, after I enter a Schengen country by plane can I travel to another country by train?
Yes, once you are in the rest of the Schengen area you can travel like anyone else, including overland. Whether you travel between Romania and the rest of the Schengen area by air or overland, you should not get an entry stamp either. The only restriction left is that there should still be border guards checking each and every person crossing the land border between Romania and Hungary, which is usually not the case inside the Schengen area.
If you have residency in a Schengen country, temporary or not, this allows you 90/180 travel in the rest of the Schengen zone. The linked thread in the other answer is rather old, and so does not address the question of borderless travel now that Romania has been admitted to the borderless zone.
Your theory should be correct, though. If you use air for travel to/from Romania, as this is now treated as borderless with Schengen countries, you should have no issue flying to say, France (you can double-check with airline or immigration, though). From France, you could take a train to Spain, no problem. You'll only want to be sure to return to Romania by air, to be sure there are no issues in case they are still doing land border control.
