SMS Ethernet Raspberry pi 2 sharing internet and receiving commands?

Question

SMS

There is raspberry pi 2, modem ZTE MF 823 Beeline, PC, Ethernet:
1) I'm interested in receiving 4G Internet on raspberry;
2) distribution of the Internet via Ethernet for PC;
3) sending SMS from PC via USB to modem in Raspberry Pi 2.
(Message is formed on PC, command is sent to AT to raspberry console, thereby activating script to send messages via modem inserted into USB)
How can I organize without crutches?
Thank you for your attention.