is it possible to have 31 slaves with 4I/4O (standard address) and 31 slaves with 4I/3O (extended address) in one network (MASTER supports extended adressing) ?

Maximim number of I/O is than 248/217 ?

Thank you very much.

Masters that support extended addressing from V2.1 > are backward compatible.
The permitted node address is 1 – 31 as you presumed.
Mixing of node types is permitted. However not as you have stated.
V2.0 < slaves have 4/4 I/O max.
V2.1 slaves have 4/3 I/O max.
The 4th output bit on a V2.1 > slave is used to select channel A or B.
Therefore a V2.0 < node uses Channel A in the master allocation table thus preventing the use of a channel B at that address as the 4th bit is used as an I/O point.
V3.0 devices multiplex the telegrams giving a larger I/O count and function as described above.
Using standard nodes max I/O count is 31 x 4/4 = 124/124
With V2.1 > nodes its 2 x 31 x 4/3 = 248/186
Mixing the types will give a value in between.