Question about Basic SMS

[vbEndUser]

Dear all,

i'm totally new to the SMS development world. I have search through the internet and trying to develop an application
which can send and receive SMS.
i have a few basic question that need to ask.

1.In order to develop an applcation to send and receive SMS, is a must to use GSM/GPRS modem?
Can we use the dial-up modem?

2.Is a must to use AT-command as well to send SMS?

3.Actually how does the GSM link to the operator? Is it when i connect to the GSM then it mean i have connected
to the operator? So i can start sending SMS.

4.from the internet, the a site saying the GSM modem is slow and manage to handler only 6 sms at a time.
If i have more that 6 sms to handler at a time, what modem should i choose?

5.Is the SDK development tools will come along together with any GSM modem brand that we purcahse?
The SDK development tools only can use for it own brand and cannot use for other.

6.Is the GSM modem's SIM card is the same with our mobile SIM card?

7.how do application receive SMS from a mobile?
Is the mobile need to key-in a phone number, in order to send SMS to my application. where do i get the number?

Thanks in advance.
vbEndUser