But who created the wallet (private company) ?
The founder of Machankura is also the creator of Exonumia, who has been in the bitcoin space for some time now.
Is it compatible to all kind of smartphones (new as old)?
Yes, USSD support is built into GSM smartphones as well. USSD is used for online banking, and many banks have either built apps today and migrated their users from UUSD, or they support both apps and USSD.