I see than T2600G-28 have new firmware V4, can V3 updated to V4. As it was for update V2 to V3 ?

Not need V3 in general :( Need just VLAN1 configurable, do it with V2 !!!

I have TP-LINK TL-SG1016DE V2. Can be updated V2 to V3 for resolve troubles with VLAN1? Firmware Version: 1.0.1 Build 20151218 Rel.58739 Hardware Version: TL-SG1016DE 2.0 Updating with...

Can T2600G do Private VLAN Trunks like it ? If Yes, how on Trunk port include TAGGED Primary and Secondary VLAN of Private VLAM members? Via GVRP?...

In additions may be need add new Interface (L3 FEATURES> Interface) and this VLAN ID link to one of port ?

I have for testing pair of T2600G-28TS from sale department of local TP-Link Company. But in testing I can' find solution how can I isolate ports inside one VLAN by my diagram. PC can't see other PC,...