How to downgrade Burp Suite to older version...?

[jaa]

You have to download the version and install manually. See the link below.

Completing the exam without Burp?

You can always install an older version of burp (1.x) , if you want the spider feature. Here is the link for Burp community Edition 1.7.36 Burp 2.x is revamped to a task based model. The spider tab has been moved. While initiating a new scan, you have the option of selecting crawl or audit. However, to initiate a new scan, it requires Pro license. So may download an older version of Burp Community Edition or rely on OWASP ZAP proxy for crawling and spider.