how able to change the sequence setting timebase to 100fps in premiere pro
If right-clicking on your 100fps clip in the bin and selecting New Sequence From Clip isn't placing it in its own 100fps sequence, you can create a custom XML sequence template to import with arbitrary values. If you save the following code as an XML file, you should be able to import it into your project and have an empty 100fps 1920x1080 2-channel sequence. 

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE xmeml&gt;
&lt;xmeml version="4"&gt;
    &lt;sequence id="sequence-1"&gt;
        &lt;rate&gt;
            &lt;timebase&gt;100&lt;/timebase&gt;
        &lt;/rate&gt;
        &lt;name&gt;Custom Sequence&lt;/name&gt;
        &lt;media&gt;
            &lt;video&gt;
                &lt;format&gt;
                    &lt;samplecharacteristics&gt;
                        &lt;width&gt;1920&lt;/width&gt;
                        &lt;height&gt;1080&lt;/height&gt;
                    &lt;/samplecharacteristics&gt;
                &lt;/format&gt;
            &lt;/video&gt;
            &lt;audio&gt;
                &lt;numOutputChannels&gt;2&lt;/numOutputChannels&gt;
                &lt;format&gt;
                    &lt;samplecharacteristics&gt;
                        &lt;depth&gt;24&lt;/depth&gt;
                        &lt;samplerate&gt;48000&lt;/samplerate&gt;
                    &lt;/samplecharacteristics&gt;
                &lt;/format&gt;
            &lt;/audio&gt;
        &lt;/media&gt;
    &lt;/sequence&gt;
&lt;/xmeml&gt;


Check out Apple's FCP XML documentation if you want to get super deep into customization, or just export an empty sequence as an XML file and have a look around. Most of the tags are fairly simple to understand as you can see. I've minimized the code here, Premiere can fill in the blanks for most settings if you don't include them.

You could actually edit your .prproj file in the same way, it's just an XML doc, but Adobe likes to obfuscate their data in base64, in addition to a few other gripes I won't get into here. It's more trouble than it's worth.