Yes, you can buy and get authentic safety shoes from credible online sources. 

Having the right equipment is key to serve the intended purpose, and hiking/trekking is no exception. If you don't have traditional hiking boots, wearing work safety shoes can be a viable option. However, it is always advisable to wear the special-purpose trekking boots.

Yes. A certified Safety Shoes will always have certification marking on it

Different variant of Safety Shoes have different shelf lives.

Refer to the relevant Standard- 
https://bis.gov.in/wp-content/uploads/2020/05/PM-IS-15298-2-cmd2.pdf

As of now we do not have safety shoes designed especially for a warm environment.

Yes, we do have Safety Shoes designed for working in wet environments. These shoes are waterrepellent and provides extreme comfort in long working hours.

Yes, we have many models of Safety Shoes especially designed for working with oil and acids

Steel toe cap is  designed to protect your foot from unanticipated injuries

Sizes are mentioned under the sole. Refer it for better fit

US Size- 3 to 13. Measure you foot size as per your standard fit.

There are two kinds of toes in Safety Shoes- Steel and Composite toe

Safety shoes can be certified from ISI (Bureau of Indian Standards) and CE (European) standards

composition of a shoe sole-PU, PU/PU, PU/Nitrile, PU/TPU, EVA/Rubber, Nitrile

Polyurethane is a chemical in liquid form and is used for making shoe soles.

A TPU is a outsole of a shoe and is made from thermoplastic polyurethane.
Benefits of TPU:
•    Rigid
•    Lightweight
•    Highly resistant to most oils and chemicals.
•    Provides abrasion resistance

Nitrile Rubber Sole is made from a type of higher heat resistant rubber which can sustains surface resistance to hot contact upto 300 degree C for one minute. Also, shooes with this sole are lightweight, flexible and offers good slip, tear, oil and abrasion resistance.

Shoes having Single Density Sole are injection moulded once onto the Shoe. Single Density outsole imparts high level of energy absorption.Shoes having Double Density Sole are injection moulded twice onto the Shoe. These Double Density outsole offer excellent abrasion resistance, slip resistance, extra comfort and flexibility

different types of shoe outsoles are as follows: PU, PU/PU, PP/Nitrile, PU/TPU, EVA/Rubber, Nitrile

 Antisistic non-woven Insole and Punture resistant Insole made from Aramid

hese are the protection classes offered by EN ISO standards. This merely refers to the extent of a hazard to which the shoe protects against.
S1 - As well as basic toe protection and slip-resistant sole, S1 means the shoe also has antistatic protection, is oil resistant and offers energy absorption in the heel. Other safety features may be added.
S2 - All of the features as S1, along with waterproof exterior so prevents water penetration and offers absorption in the upper shoe.
S3 - All of the features as S2, along with midsole penetration resistance . in simple words,  these shoes are puncture proof. For example, a steel midsole prevents sharp objects from piercing through the sole.

•    Wipe your shoes regularly with dry cotton cloth to remove the dust and enzymes accumulating on the upper surface of leather.
•    Use wax polish on your leather shoes at least once in a week. This increases the shoe life by penetrating the leather surface and protects from moisture or water spills.
•    Even water repellent shoes are not water proof, so avoid getting your shoes drenched. If they do become wet, immediately soak up the moisture inside-out using newspaper and allow to air-dry
Shoes should always be stored in a clean box or in their original shoe boxes.