RedShield Security interview questions

Very negative experience. Wildly unprofessional and a significant waste of my time. If a company treats prospective employees in this manner, I'd hate to see how they treat clients. Sat through four interviews (approximately 3 hours) to apply for a technical position. 1st Interview - 1 hour - Mixture of technical and generic/soft skill questions, nothing too complex. Attempted to gauge my experience level and figure out if I was a good fit. Went well, received a call back for a technical interview after a small wait. 2nd Interview - 1 hour - Basically an hour of technical questions, some fairly generic and others more niche. A bit more of a focus on specific toolsets. Had some good discussions and answered all questions to the best of my ability, highlighting tech stacks/toolsets which I had not worked with before. Received positive feedback within a couple of days. Was verbally offered the role, contingent on a 'rubber stamping' interview with the engineering manager. Salary package was offered and accepted, my references were contacted at this point and a slot for the final 'interview' was locked in. Was told a contract would be issued shortly. 3rd/4th Interview - 1 hour - New interview (previously uninvolved in the process to date) immediately highlighted concerns around tech stacks I was unfamiliar with. Tried to convince me to abandon the process and implied I would be a hindrance to the team and couldn't pick things up quickly enough. Attempted impromptu 4th interview at his request with 3 other staff members in tow who were not prepared. Received a take away technical test for a separate role that I felt less qualified for. Completed this test and sent through the results. Waited two days with no response until the recruiter was told that they had rescinded the offer entirely, with no explanation. Disgustingly unprofessional and rude, with no closure received.