How come car still overheating and also getting check engine code light?

Bought car used from dealer on sept. 7. Honda Civic 03 EX.

I took it back multiple times and they replaced the thermostat with a plug as well.

Head gasket and just got the car back last week on wednesday. Also I replaced the radiator cap myself.

The car continues to overheat after driving for some distance and I stop on a red light or leave car on drive on idle or parked.

Once I start to move the car again the needle starts to go down showing car cooling down. How come this still happens after getting

most of the repairs that would cause overheating?

Please help cause I will need to drive to barstow this weekend from Los Angeles.

They checked water pumps and no problem either.

Also I am getting an engine error:

P1259: Code reads:

1. VTEC System Failure
2. VTEC System B1 Failuer

After that happens, Car wont go passed 3 and if I put it on D3 (Drive 3) up hills or normal car feels like its pushing, Like it speeds up then slows down and its just going back and forth until I go back down to 3 and not using D3
Added (1). Oh and after leaving car to rest up or just turn off for a bit, car will work on D3 again and speeds up without any issues. Only if I push it up hill or a bit too fast then it does it again.

Read more: How come car still overheating and also getting check engine code light?