NoMachine 4 or 5 and NX 3.5.0 are perfectly compatibility, provided that:

1) You use SSH protocol and 'NoMachine login' to connect from a client 4 or 5 to a server 3.5.0. 

See also:
How to connect from NoMachine client 4 or later to NX Server 3.5.0
https://www.nomachine.com/AR04J00627
 

2) Your  server 4 supports SSH protocol connections if you want to connect with a NX Client 3.5.0.

Compatibility between NoMachine 4 or 5 and NX 3.5.0 software includes support for:

- Upgrade of server or client installation from 3.5.0 to version 4 or to version 5.

- Running sessions from NX Client 3.5.0 to server 4 or 5 and from NoMachine (client)  4 or 5 to server 3.5.0.

- Reconnection of virtual sessions and session migration from client 3.5.0 to NoMachine (client) 4 or 5 and vice-versa.

- Compatibility of .nxs session files 3.5.0 with NoMachine (client). Connection files version 4 and 5 are compatible with NX Client 3.5.0.

Further references:

- How to upgrade from NX 3.5.0 to NoMachine 4 or 5 and compatibility policies

https://www.nomachine.com/AR10I00603

- Instructions for upgrading a production environment from NX 3.5.0 to NoMachine 5:

https://www.nomachine.com/DT07M00092

- and from NX 3.5.0 to NoMachine 4:

https://www.nomachine.com/DT09L00072