1.Is pfsense platform that can be used for miniISP and its total free to use? Without license?

It is free of charge but to let it grow and save the future of this firewall distribution or make it done that the
development cost is able to be pay you might be free to spend each year, sometimes or often likes you want
it or you are able to do it. It on your free mind to do this and not any pressure!

To solve this you might be also able to buy hardware appliances from the pfSense shop directly matching your
criteria and workload or fits your needs and you will be also sure to get 100% compatible hardware in one act.
This might be perhaps better then fiddling your own appliance and prevent you from all problems that are pointed to this.

2.Its installed on PC like os?

Yes it is based on FreeBSD and so the best thing is to get a platform that is supported by FreeBSD for sure.

(its not windows platform)

Not no a Windows based OS or distribution, its based on FreeBSD!

and its accepted on all pc?

Not really all, but the most of them, as told above, the best is to get a platform that is supported by FreeBSD (x86_64Bit)

3.Does this platform show to users login website when they connect to wifi? (something like mikrotik)

Able to realize over the captive portal, you may also be able to set up MikroTik WiFi APs or UBNT APs as well for your
usage.

4.Does it have billing? And can i connect users between 2 3 pfsense machines?

You may able to use the Captive portal together with a voucher system and set up different groups for the Internet access.
Together with UBNT (Ubiquiti) WiFi Access Points
UCRM-Complete WISP management platform
Together with MikroTik WiFi Access Points
Handlink-ISS 7000 v2
[Handlink-HotSpot printer[]

5.And can i make vouchers?

Yes you can, together with the Captive Portal.

At moment im on Kerio Control but pfsense look very very better solution.

pfSense is a software based firewall distribution, that can be turned over a packet management into a fully featured
UTM device, acting as a load balancer, BGP router, HA solution or a pure firewall, likes you want and the hardware is
able to do.
IDS/IPS - Snort & Suricata
geoIP blocking, (Spam and Malware) - pfBlockerNG
AV Scanning - ClamAV
Proxy Server - Squid, SquidGuard & SARG
RadiusServer - FreeRadius 2.0
and many others.](https://www.handlink.com/products_WG-500P-P.php)

It can be installed on a PC and it is freebsd

For login page and vouchers yes use captive portal

"can i connect users between 2 3 pfsense machines?"

you mean from different locations? If yes use site to site VPN