1. Does sending someone solo after tailwheel differences training count?
Count for what? In order to do differences training the person must be a licence holder so no FI involvement at all in any solo flight.
2. Does training time and sending-solos in a microlight school count if done using an EASA FIC?
No, the EASA regulation does credit experience on Microlights towards EASA licences and certificates. In the latest amendment to Part FCL, experience on 3 axis microlights may be credited towards the 12 hours required for revalidation by experience, but the dual training is only acceptable in a SEP Class aircraft.
FCL.035
(a) Crediting of flight time
(1) Unless otherwise specified in this Part, flight time to be credited for a licence, rating or
certificate shall have been flown in the same category of aircraft for which the licence, rating
or certificate is sought.