Depends on the tread depth of the 3 old vs 1 new tire. The potential issue is in regards to your center differential, long term changes in the tire diameter is really hard of that differential and can easily cause premature failure.
I believe 2/32" is about the limit for tire tread differences before it gets risky.
Yes depends on tread depth difference. Also, u can cheat a little with tire pressures to eliminate "some" depth difference. A lb or two up in the old ones and the same lb or two down in the new one will bring the radii closer to the same.