Yes, you can crack rank below 1000 in jee mains in 6 months. Jee is all about speed and accuracy. If you have strong basics and formulas on tips then you will be able to crack. Practise allot of questions to understand the pattern and exceeding your speed. Practise to manage time and how much time you should devote to particular section.

Yes, six month of vigorous preparation is enough for cracking JEE MAINS with rank under 1000. JEE mains is all about speed,accuracy and consistency. Anyone who masters in all the three can easily crack JEE MAINS.

Question asked in JEE MAINS are not hard. Only 2-3 questions in each PCM are hard and rest of questions are of easy and moderate level. 

For cracking any exam, first you need to know the pattern of exam. Questions asked in JEE MAINS are of same trends that were asked previously. You just need to work on important topics for this exams like among 30 questions in physics ,3 -4 questions were asked only from MODERN PHYSICS and ELECTROSTATICS. Like this you need to analyze the syallabus of JEE MAINS wisely and do hard work and victory is yours.

Best of luck