Hi,

1. For any newly diagnosed disease (i.e. after taking the policy, after enhancing the SI, adding riders etc.; basically after your last update to the policy), you need not declare to the insurer. It won't harm even if you disclose. But when you do any further upgrade, rider addition, plan changes, etc. you'll need to disclose about it. And keep your prescription/reports handy as the insurer may ask for those at the time of claim.
2. If your policy has additional loading because of your smoking condition, and since you quit it now, it may help if the insurer is ready to remove that loading.

Thank you